Servos to the Rescue
Can servos be used to dramatically reduce maintenance costs?
This article from Control Design suggests the answer is a
big “yes”:
http://www.controldesign.com/articles/2005/251.html
Summary:
K.I.S.S (keep it simple, stupid) — basically, the less
mechanical parts, the better. “R.A. Jones has been building
cartoner packaging machines for 100 years. In its new
cartoner machines, the company changed over to servo drives
to reduce the number of mechanical components and increase
reliability….By using servos, R.A. Jones reduced its
engineering costs and built a flexible, high-reliability
cartoner that compresses installation time and reduces
maintenance by eliminating belts, drive chains, line shafts,
pulleys, sprockets and torque tubes.”
Tom Matyas, product manager for drives, motors and motion at
AutomationDirect says:
- lineshafts work well, but require too much service: “Due
to their mechanical nature they rely a great deal on correct
machine setup, such as synchronization and mechanical
connections, plus proper maintenance…. This usually means
longer setup between cycles on machines that run several
different products. Improper setup and/or mechanical wear at
a single station may have a ripple effect on any station
connected, thereby affecting the efficiency and performance
of the entire system.”
- “Converting rotary motion into linear motion requires, at
minimum, a rotary motor, gearbox, two pulleys, a belt,
couplings, a ballscrew and zero-backlash nut, and linear
bearings and races.”
Servos, direct-drive technology, linear drives and
variable-speed motors are all desirable for
equipment-building engineers due to their mechanical simplicity.
Mike Wagner, business development team leader, Global OEM
Team, Rockwell Automation notes:
- “The move to servos and integrated control technology has
the potential to replace up to 60% of the mechanical parts
in a machine.”
- “The benefits of this reduction include lower costs,
increased reliability and maintainability, as well as
improving machine performance by up to 75%. For example, in
the past it took several hours to change over a machine to
run a new part, and the machine could only run a few product
variations. Today, servo-driven machines complete
changeovers in less than two hours, and now you can run
hundreds of product variations on a single machine.”
Servos are very flexible to use and make a key differences
in such applications. For example, in current-load apps,
important feedback is easily acquired. Servos also
“eliminate contactor replacement due to arcing when full
voltage starting. The acceleration and deceleration reduces
mechanical system shock at startup extending the life of
mechanical components.”
Tom England, marketing manager of the direct-drive motors
business unit at Danaher Motion, reports direct-drive
technology simplifies operation:
“Machine control using direct-drive technology provides
significant improvements in machine uptime due to the
elimination of the mechanical transmissions, gearboxes, and
timing belts… Machine simplification also is greatly
enhanced by the elimination of all the components needed,
such as brackets, mounting parts, and tensioning components.
Most high-speed pick-and-place machines employ direct-drive
technology today due to the speed performance and
reliability improvements.”